Air laying system having a seal roll



May 5, 1970 w. R. FURBECK AIR LAYING SYSTEM HAVING A SEAL ROLL 2Sheets-Sheet 1 Filed Oct. 5; 1967 lNVENTOIZ v WW7? 2 I a/666% BY WW Wdik, ATTvs.

May 5, 1970 w. R. FURBECK AIR LAYING SYSTEM rmvxne A SEAL ROLL 2Sheets-Sheet 2 Filed Oct. 5, 1967 1 N v E N TO 2 Name/7 F. awe

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l l l |L| I. I. llrlllllllllmlll United States Patent 3,509,604 AIRLAYING SYSTEM HAVING A SEAL ROLL Warren R. Furbeck, Knoxville, Tenn.,assignor, by mesne assignments, to International Paper Company, NewYork, N.Y., a corporation of New York Filed Oct. 3, 1967, Ser. No.672,477 Int. Cl. D0lg 25/00 US. Cl. 19--156.3 7 Claims ABSTRACT OF THEDISCLOSURE A stream of air carries loose fibers through enclosed ductsand deposits them on a continuously moving carrier as it moves through agenerally enclosed chamber. The carrier and now formed fibrous pad exitthe chamber through an opening which is sealed by a unitary seal roll.The seal roll is provided with a groove corresponding to the contour ofthe pad and is slightly embedded in the pad to seal against air leakagewhich would cause an undesirable movement of the fibers in the chamber.The seal roll is rotated so that its walls defining the groove have atangential velocity which differs from the linear velocity of the padand carrier whereby the fibrous surface of the pad is brushed and workedby the roll.

This invention relates to an air-laying system for producing a contouredweb or pad from a quantity of loose fibrous material and moreparticularly to an improved apparatus including a seal roll for workingthe fibrous material while sealing against leakage of air therebypreventing an undesirable movement of fibers by the leaking air.

In an air-laying process, a stream of air carries fibers throughsuitable, enclosed ducts and deposits them on a continuously movingcarrier as it travels through a generally enclosed} forming chamber. Thefibers are filtered from the air stream by the carrier and may be formedby appropriate methods into a predetermined contour on the travelingcarrier. For example, in copending application S.N. 507,089, entitledForming Apparatus, a process is described in which fibers of wood pulpare laid on a carrier formed by a continuous web of creped tissue aspart of a process of fabricating a disposable diaper pad which has acentral portion thicker than adjacent flanking or side portions. Threeseparate seal rolls, one for each of the respective flanking portionsand one for the central portion of the pad, extended to the fibrous padand slightly comp-acted the pad traveling beneath the respective rolls.All of these three rolls were of the same diameter and separately drivenat the same speed providing a tangential velocity equal to the linearvelocity of the pad and the carrier. Although the adjacent ends of therespective rolls were disposed close to one another, air leaked betweenthem. Also, fibers were pinched between the adjacent roll ends and beganto gather in the space between the roll ends. This impeded the freeturning of the rolls. Eventually these fibers accumulated to the pointwhere it was necessary to remove them.

In a disposable diaper pad, relatively large quantities of fluid must bequickly absorbed and distributed to prevent flooding and leaking fromthe diaper. To achieve maximum absorption and distribution in aninexpensive manner, the air-laid pads are formed with a predeterminedcontour, a uniform cross-sectional thickness and a predetermined fibercompaction. Under the present invention, the air-laying apparatus formsa pad with such qualities and includes a novel seal roll constructionwhich engages the pad with a light pressure and which gently screeds thefibers to provide a uniform cross-sectional thickness at least over thethicker and more absorptive part ice of the pad. The seal roll gentlycombs the fibers at the surface of the pad to provide a relativelysmooth outer surface on the pad. The seal roll, as its name implies,performs the function of sealing the apparatus against air leakage andthereby prevents a resulting deleterious movement of fibers by ambientair rushing into the forming chamber. The invention also provides a muchsimpler construction of seal roll and the drive therefor, using but aunitary seal roll to provide the sealing previously requiring threerolls.

Accordingly, a general object of the invention is to provide an improvedair-laying apparatus for forming a fibrous web having a controlleddensity and shape.

Another object of the invention is provide a simpler and more economicalconstruction for a seal roll and the drive therefor.

Other objects and advantages of the invention will become apparent fromthe detailed description taken in connection with the accompanyingdrawings in which:

FIGURE 1 is an elevational view of an air-laying apparatus embodying thenovel features of the present invention;

FIGURE 2 is an enlarged, fragmentary view of a seal roll shown in FIGURE1;

FIGURE 3 is a fragmentary sectional view taken substantially along theline 33 of FIGURE 2;

FIGURE 4 is a fragmentary, partially sectioned view of a seal rollconstructed in accordance with another embident of the invention; and

FIGURE 5 is a transverse, cross-sectional view of the fibrous pad madeby the apparatus of FIGURE 1.

As shown in the drawings for purposes of illustration, the invention isembodied in an air-laying apparatus 11 which forms a continuous web orpad 13 (FIGURE 5) of a predetermined shape from loose fibrous materialsuch as wood pulp fibers. In this instance, the fibrous pad is formedwith a central longitudinally extending portion 15 which is thicker thanadjacent, longitudinally extending flanking or side portions 17. In atypical diaper, the central wide portion 15 may be 3 inches in width andabout A inch in depth while the overall width of the pad isapproximately 14 inches. The depth of the side portions is about A: ofan inch. The present invention, however, is not limited to anyparticular size or contour of pad as the dimension and contours may varywith different embodiments of the invention.

Very generally, the illustrated apparatus employs a pair of air-layingunits 19 and 21 (FIGURE 1) each of which forms a part of the fibrous pad13. In this instance, the first unit 19 deposits a narrow 3 inch stripof fibrous material slightly more than of an inch in depth and thesecond unit 21 overlays on this strip a 14 inch wide layer of fibersslightly more than A; of an inch in depth. After passing the second unit21, the small, thick central portion 15 is about inch deep and the wide,thin flanking side portions 17 are about /3 inch deep as the pad leavesthe outlet end (the right hand side in FIGURE 1) 0f the airlayingapparatus 11.

Each of the tandem units 19 and 21 is generally the same except for itsseal rolls, as will be explained later. Thus, each unit is provided Witha shredder 23 and connected refiner mill 25 which defibrate felted websof wood pulp (not shown) into individual fibers or as close thereto aspossible. The individual fibers are carried by an airstream down througha duct 27 to the upper end of an enclosed, forming chamber 29 throughwhich travels a web 31 of creped tissue on an endless meshed beltcarrier 33. Vacuum boxes 35 are disposed beneath the upper runs of thecarrier 33 and are connected in a suitable manner to a vacuum source topull the air through the creped tissue web and the meshed belt. Thefibers in the air stream are filtered onto the upper surface of thecreped tissue web 31 as the air passes through the web and into thevacuum boxes. The web and pad move longitudinally from left to right(FIGURE 1) through suitable slots, such as the slot 32 (FIGURE 2) ineach of the end walls of the enclosed chamber 29. These slots are sealedby suitable seal rolls 37a, 37b, 37c and 37d, which may have differentcontours as will be described in detail.

The present invention is of particular utility in producing air-laid,wood pulp fiber pads which have a substan' tially uniform density andcross-sectional thickness in each of several portions and 17 so as toprovide a lightweight, soft and highly absorbent pad. If the fibrousmate rial is too heavily compacted, the pad will not quickly absorbfluids and distribute them with the result that the pad and the diapermay be overloaded with fluid which will leak or strike through the pad.Also, if some of the portions 15 or 17 are formed with less than theprescribed cross-sectional thickness, there may not be enough fibers toabsorb and distribute the fluid being received by the diaper. On theother hand, if the pad has portions which are thicker than thatrequired, an excess of fibers is provided beyond that needed forabsorbency and this results in an unnecessary increase in cost of thepad. Hence, a uniform cross-sectional thickness and density is desiredwithin the respective center and flanking portions 15 and 17 of the pad.

In accordance with the present invention, the air-laying apparatus isprovided with an apparatus which provides a more uniform thickness forthe pad, particularly at the thicker portion of the pad, by gentlyscreeding the fibrous pad as it leaves the seal roll 37d at the outletend of the forming unit 21. To limit the amount of compacting, the sealroll is lifted by springs. To screed the pad, the portions of the sealrolls engaging the pad have a tangential velocity which is less than thelinear speed of the pad whereby the roll exerts a retarding force on thefibers it engages and causes a gently combing or brushing of the top ofthe pad. As a result, fibers at the high points and the thicker areas ofthe pad are redistributed to lower points in the pad and a smoothersurface is obtained. As will be explained in greater detail, anotherfeature of the invention is a simplified, unitary seal roll and a drivefor the roll.

Proceeding now with a more detailed description of the invention, thetandem forming units 19 and 21 are supported by a main frame 39 with theshredders 23 disposed on upper beams and over the refiners 25. A feltedwood pulp web (not shown) of a predetermined moisture content is fed toeach of the shredders 23 which chop the webs into postage-stamp sizepieces which are then fed through vertically disposed ducts 41 leadingdown to the refiner mills 25 which then grind and break the pieces intoindividual wood pulp fibers or as close thereto as possible. Streams ofmoving air carry the fibers through the ducts 27 and into the interiorof the generally boxedshaped, enclosed chambers 29. The latter aregenerally hollow with an open, lower end disposed across and closelyadjacent to the creped web 31 and carrier 33 which pass through inletand outlet slots 32 formed in the respectively vertical end walls 43(FIGURE 2) of these chambers. These slots extend considerably above theweb 31 and their upper edges are defined by a wall 44 (FIG- URE 2) whichis adjacent the periphery of one of the seal rolls 37a-37d. Each of thechamber side walls is sealed and connected to a vacuum box below. Thevacuum boxes 35 are ducts connected to suitable sources of suction (notshown). Preferably, the vacuum boxes 35 are formed by vertical sidewalls 46 (FIGURE 2) defining a box-like chamber beneath the formingchamber 29. At the top of the vacuum box is a carrier support 48 in theform of an expanded metal screen having very wide openings to allow theair to pass easily without disturbing the fiber deposition on thecarrier. The seal rolls are aligned over the end walls 46 of the vacuumchamber to provide a better sealing action with the vacuum chamber andwith the supported pad disposed on and supported by the walls 46 at thesealing rolls.

The entrained fibers are filtered by the creped tissue web 31 from theair moving into the vacuum boxes. The web 31 is drawn from a largesupply roll 47 (FIGURE 1) and is disposed over the upper surface of thetop run of the endless carrier belt 33 and moves with the latter throughthe respective chambers and then leaves the carrier to move to the nextstation (not shown) for further processing in forming the disposablediapers. In this instance, the web 31 is approximately 30 inches inWidth and the endless mesh belt 33 is slightly larger in width. The belt33 is trained about a drive roll 49 rotatable about a generallyhorizontal axis and driven by a chain 51 extending to a gear unit 53which in turn is driven by a drive shaft of the diaper-making machine(which is not shown). The mesh belt 33 extends from the drive roll 49 toan idler roll 55 and the upper run of the belt is disposed in agenerally horizontal plane for travel through the tandem units. A pairof belt tension rolls 57 hold the endless carrier belt 33 at the propertension.

To seal the slots 32 against the entry of air into the chamber, which isbelow atmospheric pressure, an inlet and outlet seal roll are providedfor each of the enclosed chambers 29. Each of the seal rolls 37a37d ismounted in an identical manner, therefore, the mounting of only one sealroll 370 is illustrated and discussed in detail. As best seen in FIGURES2 and 3, seal roll 37c is mounted for rotation by stub shafts 61disposed in a pair of bearings 63 carried by support arms 65. Therotational axes of the seal rolls are disposed generally horizontallyabove and parallel to the web 31 and are disposed normal to the path ofweb travel.

Adjacent the respective ends of the seal roll 370 are end seals 69(FIGURES 2 and 3) of L-shaped configuration with vertically extendinglegs fastened to the housing wall 43 adjacent the vertical sides of theslots 32. The end seals 69 project outwardly from the housing wall 43 topositions closely adjacent the radial end walls of the seal roll 37c.Extending across the top of the seal roll 37c and disposed between theend seals 69 is flexible doctor or seal blade 71 which is fixed to thewall 43 above the slot opening 32. The doctor blade extends outwardlyfrom the wall 43 into engagement with the rotating, upper peripheralsurface of the seal roll. Preferably, the doctor blade is contouredalong its free edge 73 to fit into grooves formed in the seal roll 37c.Thus, the doctor blade and the end seals prevent sideways and overheadentrance of air or the loss of fibers from the slot 32. As the lowersurface of the roll 37c is embedded in the pad, it alleviates the lossof air pressure at the interface of the seal roll and the pad andreduces any inward flow of ambient air to a volume and flow rate whichwill not disturb the velocity profile of the air stream within theforming chamber 29. That is, a large leakage of ambient air beneath theseal roll and into the chamber could roll fibers from the pad back intothe chamber and also disrupt the air stream profile within the chamberand thereby disrupt the pad contour.

In the preferred embodiment of the invention, the seal rolls alsofunction as web feeding rolls in that the web 31 is gripped in the nipbetween the seal rolls and the belt 33 and they combine to strip the webfrom its supply roll 47 and then feed the web through the tandem units.To feed the creped tissue web 31 without wrinkling or tearing, the sealrolls may be formed with a resilient layer 77 (FIGURE 4) for pressingagainst the web 31 and belt 33. More specifically, the seal rolls mayhave a layer of rubber inch thick fixed about a cylindrical metallicsleeve 78 for the seal roll.

The axial end portions of each seal roll are of equal diameter and arerotated at the same peripheral speed to feed the web 31. To rotate therolls 370, there is provided a drive train which includes a sprocket 79(FIG- URE 3) fixed to stub shaft 61 and a driving chain 81 extendingfrom the sprocket 79 to another sprocket 83 fixed to a support shaft 85journaled in bearings 87 (FIG- URE 3) on the lower end of vertical framemember '89. The free end of each support shaft 85 is provided with aworm gear 91 which is meshed with a suitable gear 93 carried on acommon, horizontal drive shaft 95 extending longitudinally of thecarrier 33 between the seal rolls. At its left end (FIGURE 1) the shaft95 is connected to and driven by a gear box 96 driven by a chain 97extending to the drive sprocket for the carrier drive roll 49. Becausethe carrier 33 and the seal rolls 37a37d are all driven by the gear unit53, the speed of the carrier web may be correlated with the rotationalspeed of the seal rolls such that the tangential speed of the seal rollsengaging the web 31 matches that of the linear speed of the carrier 33.

While the seal rolls 37b and 370 function to shape the inner portion ofthe central area of the pad, it is the last seal roll 37d which does thefinal contouring and fiber combing for the finished pad 13. Inaccordance with the preferred embodiment of the invention, this sealroll 37a is in the form of a unitary roll having a central groove 101about three inches wide (FIGURE 4) with a diameter which is about inchless than the diameter of outer end portions 102 of the roll. Thecentral groove 101 is flanked by grooves 105 which are inch deep andextend laterally about five and one-half inches from the groove 101 toan annular shoulder 106. The tangential speeds of the roll at thegrooves 101 and 105 are deliberately designed to be slower than thelinear speed of the web 31 and the pad 13 so that these smaller diameterportions exert a retarding force on the pad fibers they contact. Theretarding force causes a screeding of fibers on the upper surface of thepad.

It has been found that the smaller diameter portion at the groove 101 isparticularly effective in providing a gentle combing or screening of padfibers where the pad is relatively thick. This assures a smoother uppersurface, a more uniform thickness and a more uniform density for thecentral portion of the pad which is of primary importance to theabsorptive characteristic of the pad.

As these seal rolls are of unitary construction, the more complicatedarrangement of separate drives for each of the flanking and centralportions has been eliminated. Also, the pinching of fibers between rollsas previously employed, is avoided as well as the loss of any airbetween the radial faces of those adjacent rolls.

In this instance, the pressure of the seal rolls on the pad is regulatedby biasing means which are in the form of individual springs havingattached scales 107. The springs are fastened at their lower ends to thepivotally mounted bracket arms 65 for the seal rolls and attached atupper ends to a horizontally disposed, stationary frame member 108(FIGURE 1). The springs are adjustably mounted so that the force withwhich the rolls engage the pad can be limited to a predetermined portionof the weight of the rolls 37a-37b and their respective pivot arms 65.In the preferred embodiment of the invention, the seal rolls apply alight even pressure to the pad 13 just sufiicient to embed the roll inthe pad and stop any large volume of ambient air from moving under theroll.

To prevent pickup of fibers on the seal rolls from the fibrous pad, therolls may have an outer layer of plastic material disposed on theresilient layer 77. A film of .0005 inch of polytetrafluoroethylene assold under the trademark Teflon has been applied to the outer surface ofthe roll and has worked satisfactorily.

It will be appreciated that the various seal rolls 37b- 37d areconfigured with annular groove of a depth and width to correspond to theparticular shape of the pad at the line of its passing beneath the roll.Thus, the seal rolls at the outlet side of the first tandem unit 19 andthe inlet side of the second tandem unit 21 have only a3 inch widecentral groove 113 (FIGURE 3) which is about inch in depth. Because theinlet seal roll 37a for the first tandem unit 19 seals against the web31 only, it is not provided with any annular groove and has anuninterrupted cylindrical surface and a uniform diameter across its fulllength.

As an aid to understanding the invention, a brief description of theoperation of the invention is provided. The creped tissue web 31 isdisposed in the nip between the seal rolls 37a-37d and the upper surfaceof the continuous carrier 33. The seal rolls engage the outer side edgesof the creped tissue web and as they rotate they strip the web from thesupply roll 47.

As the web 31 passes through the first tandem unit 19, air-borne fibersmove through the duct 27 into the enclosed chamber 29 and deposit on theweb to form a pad of fibers three inches wide. The air stream carryingthe fibers moves through the web 31 and the meshed carrier 33 into thevacuum box 35 beneath the web and carrier.

Simultaneously, at the other tandem unit 27, a 14 inch wide pattern offibers is being overlaid on the incoming 3 inch strip.

Each of the seal rolls 37a37d is driven at the same speed by a commonshaft 95 which, in turn, is driven by the drive 53 for the carrier 33 sothat the seal roll portions engaging the web 31 have a tangential speedequal to the linear speed of the carrier 33.

To control the amount of pressure exerted by the roll on the pad andthereby the amount of fiber compaction and embedding by each seal roll37b37d, each seal roll is pivotally mounted for pivoting about a supportshaft and is lifted upwardly by an associated spring having a scale 107.The latter lifts a predetermined portion of the weight of the roll sothat the roll engages the pad with a light yet predetermined force.

The last three of the four seal rolls, namely, 37!), 37c and 37d extendinto engagement with the fibrous pad 13 on the web 31 to provide a lowerseal preventing the loss of air pressure and fibers along the carrierand web from the slots 32 in the housing 29. At the opposite ends of theseal rolls, end seals 69 are fixed to the enclosing chamber wall 43 andextend to the radial end faces of the rolls. The slots 32 are furthersealed at the top of the roll by the flexible blades 71 extending fromthe housing wall 43 to engage the respective rolls.

The smaller diameter portions of the seal rolls, particularly seal roll37d, effectively screed and comb the pad while compacting the same toprovide an improved air-laid fibrous pad 13. Because the tangentialspeed of the smaller diameter portion 101 of the seal roll 37d is lessthan the linear travel speed of the pad 13 with which it is in contact,this roll portion exerts a drag or retarding force on the upper fibersof the pad tending to screed off any excess fibers and to fill in anyareas Where the pad is relatively thinner in cross-sectional dimension.

Best results are obtained by the direct positive driving rotation of theseal rolls 37a-37d by the line shaft 95. Less satisfactory, but adequateresults have been obtained without using such a positive drive. Forinstance, the seal rolls may be rotated solely by the carrier 33 againstwhich the rolls are biased. Thus, the rolls will, except for anyslippage, have a tangential velocity equal to the linear velocity of thecarrier 33.

From the foregoing it will be seen that the air-laying apparatusprovides a pad with an improved outer surface, a more uniform densityand a more uniform crosssectional thickness. Also, the seal rollconstructionsmay be greatly simplified and easily driven through asimple and less complicated driving arrangement. Although the seal roll37d is shown and described in connection with a pair of tandemair-laying units, it will be appreciated that this roll could be alsoemployed in a non-tandem airlaying apparatus where the entire pad isformed in one unit rather than in a pair of units.

While a preferred embodiment has ben shown and described, it will beunderstood that there is no intent to limit the invention by suchdisclosure but, rather, it is intended to cover all modifications andalternative constructions falling within the spirit and scope of theinvention as defined in the appended claims.

What is claimed is:

1. In an apparatus for continuously air laying a fibrous material on amoving carrier and forming a pad of nonuniform cross sectional thicknessincluding a longitudinally extending portion having a thicknesssignificantly greater than the thickness of an adjacent flanking portionextending in the same direction, said apparatus comprising means forforming said pad and including at least one chamber in which fibers arecarried by an air stream and are deposited on said carrier, said chamberhaving an opening through which said carrier and pad leave said chamber,a unitary'seal roll mounted for rotation about an axis disposedtransversely of said pad movement and disposed to seal said opening byengaging said pad and closing said opening, adjacent portions of saidroll having different diameters to define a first groove aligned withsaid longitudinally extending thicker portion of said pad and having adepth to accommodate the same while engaging the surface thereof andsecond groove aligned with said flanking portion of said pad and havinga depth to accommodate the same While engaging the surface thereof, andmeans for rotating said roll about its axis with the smaller diameterportions of the roll having a tangential velocity less than that of thelinear velocity of said pad whereby said smaller diameter portions brushfibrous mate rial on the surface of said pad.

2. An apparatus in accordance with claim 1 in which said fibrousmaterial is deposited onto a creped tissue web carried by said carrierthrough said chamber, and in which larger diameter portions on said rollengage said web and cooperate with said carrier to feed the web withoutwrinkling or tearing the same.

3. An apparatus in accordance with claim 1 in which means are providedto mount said seal roll to limit the pressure with which the seal rollengages the fibrous pad and said carrier.

4. An apparatus in accordance with claim 3 in which said mounting meansincludes means to mount said seal roll for pivotal movement toward andfrom said pad and biasing means for the pivotal movement of said sealroll and the pressure with which the roll engages the pad.

5. An apparatus in accordance with claim 1 in which 8 said seal rollincludes an inner shaft, a layer of resilient material on said shaft forcushioning the compressive force of said seal roll, and an outer surfacelayer of plastic on said resilient layer to limit the amount of fiberspicked up by the seal roll.

6. An apparatus for continuously air laying a fibrous material to form apad of non-uniform cross sectional thickness including a longitudinallyextending portion having a thickness significantly greater than thethickness of an adjacent flanking portion extending in the samedirection, said apparatus comprising a moving carrier for receiving andcarrying a fibrous material along a predetermined path of travel at apredetermined velocity, means including first and second substantiallyenclosed chambers spaced along said path of travel for conducting airstreams bearing fibrous material to said carrier, each of said chambershaving inlet and outlet openings through which said carrier may travelas it moves along said path, seal rolls mounted for rotation at each ofsaid inlet and outlet openings, said seal rolls at the inlet slot of thesecond chamber and at outlet slot of both of said chambers each havinggrooves therein to accommodate said portions, said seal roll at theoutlet opening of said second chamber having a first groove aligned withsaid longitudinally extending thicker portion of said pad and having adepth to accommodate the same while engaging the top surface thereof anda second groove aligned with said flanking portion of said pad andhaving a depth to accommodate the same while engaging the surfacethereof, and means to rotate said seal roll at the outlet of said secondchamber so that at least one of the grooves therein has a velocitydifferent than said predetermined velocity of said carrier.

7. An apparatus in accordance with claim 6 in which each of said sealrolls is a unitary roll and in which the outlet seal roll for the firstchamber and the inlet seal roll for the second chamber each have anidentical groove lo cated centrally of the roll, and in which saidoutlet seal roll for the second chamber has a similar groove and isflanked by additional side grooves.

References Cited UNITED STATES PATENTS 2,057,167 10/1936 Sherman 161l24XR FOREIGN PATENTS 23,675 1894 Great Britain.

DORSEY NEWTON, Primary Examiner

